The present invention relates in general to the field of liquid spray coating, and in particular to a new and useful apparatus and method for spray coating a lengthy substrate which is moving at high speeds.
When an electrostatic preventive coated film is to be built up onto the surface of lengthy substances such as magnetic tape, it is necessary to perform this process extremely efficiently when applying it to industrial production.
A conventional technique is known where fine grain diameter mists are produced through the use of a supersonic wave oscillation device, which mists are then sprayed onto the surface of an object. This method, however, involves some problematic aspects that are given below.
(1) One oscillation device cannot produce so much volume of mists (hereinafter referred to as "fine particles"), so a number of oscillation devices must be installed for producing a great deal of fine particles that can be utilized for industrial purposes. For instance, the volume of fine particles that can be produced by a supersonic wave oscillation device is only 0.1 miter/hour on the basis of water as the liquid to be sprayed.
(2) While using a supersonic wave oscillation device, the liquid level must be controlled severely and its negligence leads to breakage of the device.
(3) The device cannot be used over a long period of time even though its costs are comparatively high.
(4) The device cannot be used with a liquid of high temperature.
(5) For the aforesaid reasons, the spraying method utilizing a supersonic wave oscillation device cannot be applied to the case where a silicone emulsion coating is to be made on the surface of a plastic film or to the case where electrostatic inhibitor water soluble liquid is to be sprayed in large volume and at industrial scale, onto the surface of magnetic tape.